I'm not ingame very much but I have a few.
I don't know why, but it bothers me when people put "M" or "F" at the end of their name. I could understand if you can't tell by the name which gender your character is, but if you had a name like "David" and added "M" at the end of it... No female would be named David, so the "M" part is unnecessary. But I've seen this before. I put that sort of information in the bio section. Nothing against those who do it, I just get irritated by it.
I also dislike how I'll glitch into certain objects if I run up them instead of jump up them, and everyone should know which objects those are... XD
Super-laggy patches on maps. Not that my maps don't have these, which they do...
When I glitch out of my building maps and can't get back in because there are no holes in my roof.
When a map server ceases to work and as soon as I put a blocker in front of the portal, the map starts working again.
Random game crashes when I turn the camera completely upwards while working on a map.
...Most of these are map related XD